I love the MadDog rifle stock. It moves the strain from using the bottle as a shoulder rest to the stock, and it eliminates any inaccuracy issues that result from the flex at the frame where the bottle and the valve assembly meet.
As fas as the regulator goes, the PCP Tunes V3 or the PCP Tunes Texan reg are the best for the Condor. If you're shooting a big bore version, I'd go with the Texan reg (i.e .257 to .357). Don't bother trying to regulate anything bigger. You'll be robbed of power. But the plenum on the Texan reg is huge. The V3 reg is more for smaller caliber AF platforms, but as it's name indicates, it's the 3rd version of the original. It has a larger plenum than the original reg, and it has a CRAZY washer Belleville washer stack that has very tight tolerance and is highly adjustable. It can handle 300 BAR fill pressure at the bottle, and can be adjusted to 250 BAR on the regulator side. I have mine set at 210 BAR, and I'm pushing 38gr .254 AVS slugs at 965-973 fps (about 80 FPE). I have a custom barrel on my rifle however. It's a un-choked Russian Republic barrel that is .247/.252 land/groove diameter with a 1:15 twist.
Regarding what slug shoots best, that will vary from gun to gun, even 2 identical guns. The barrel either likes a slug, or it hates it. When shooting a slug from your rifle for the first time, you're going to need to buy some sample packs from different manufacturers. So if you're using the stock Condor LW barrel, it's got a twist of 1:17.7 and a land/groove diameter of .248/.254. I use the 38gr cup base slug from AVS slugs in .254 diameter. My barrel loves them. But I spent a lot of money with sample packs trying to find the slug the barrel likes. I particularly like AVS slugs because of the larger diameter size that concentrically seals the grooves of my barrel. If you're interested in AVS slugs, and you're shooting a .25 rifle, I would recommend a sample pack of .2503 and .254. I'd recommend ordering cup base in all weights 30gr, up to 48. Might cost you $80-$100, but well worth it.